"The horse is 100 per cent sound and giving off all the right signs. But he had a little bit of heat in his leg tonight and though he jogged up sound on a hard surface, there is a small hole in his off-fore suspensory.

"It's a blow as he's our flag-bearer, but the horse is happy and healthy and the vet is cautiously optimistic that it should heal in time."

Big Orange defeated Order Of St George by a short head in a dramatic finish to the 2017 Ascot Gold Cup.

He was last seen finishing down the field in the Dubai Gold Cup at Meydan in March and was preparing to make a return to the track in the Henry II Stakes at Sandown on Thursday week.

Big Orange finished fifth in the 2015 Melbourne Cup and 10th the following year.